This invention concerns a nozzle used to direct a flow of oil under pressure toward a part of an internal combustion engine. The invention also concerns a lubrication system for an internal combustion engine including, amongst others, at least one such nozzle. Finally, the invention concerns an internal combustion engine equipped with a nozzle or a lubrication system as mentioned here-above.
In order to lubricate moving parts of an internal combustion engine, it is known to use a pump which feeds oil to different locations in the engine. Such a pump represents an important part of the overall engine friction, often between 10 and 20 percent. Oil provided by the pump can be used to feed a support interface for a crankshaft of the engine. It can also be used to feed one or several piston cooling nozzles or jets adapted to direct the flow of oil under pressure toward the underside of a piston of the internal combustion engine. The flow of oil coming out of such a nozzle must have a flow rate and a speed adapted to efficiently cool the piston.
FR-A-2 861 321 discloses a piston cooling nozzle provided with an elastically deformable ring which adapts the outlet section of the jet, depending on the flow rate of oil. With such a device, the speed of the oil flow cannot be controlled independently of the oil pressure which depends on the rotation speed of the engine. In some circumstances, it is desirable to adapt the oil speed independently of the rotation speed of the engine.
On the other hand, it is known from EP-A-1 362 993 to feed piston cooling positions with oil coming from a pump through a control valve which can be open or closed depending on a lubrication strategy. This allows correcting the influence of the rotation speed of the engine but does not permit to independently adjust the flow rate and the speed of oil coming out of a piston cooling jet.
On the other hand, in some working conditions of an internal combustion engine, e.g. under partial load or in idle conditions, oil can be provided to a piston cooling nozzle with the relatively low pressure, with a risk that the speed of the oil flow or jet coming out of the nozzle is not sufficient to reach the corresponding piston or to fill its cooling gallery.
Similar problems occur with nozzle used to inject oil toward other parts of the engine.
It is desirable to provide a nozzle adapted to efficiently direct a flow of oil toward a part of an engine even when its is fed with oil under relatively low pressure. In particular, the invention provides, according to an aspect thereof, a nozzle which enables to independently control both the oil flow rate and the oil speed in the jet of oil coming out of its outlet, which leads to an optimized cooling of the piston.
The invention concerns, according to an aspect thereof, a nozzle adapted to direct a jet of oil under pressure toward a piston of an internal combustion engine, this nozzle having a variable outlet section. It is characterized in that it is provided with mechanical means adapted to control its outlet section on the basis of the pressure of a fluid under pressure provided to these mechanical means independently of the flow of oil going through the outlet of this nozzle.
Thanks to an aspect of the invention, the mechanical means, which are piloted by the pressure of the fluid, can adjust the outlet section of the nozzle in order to adjust the speed of the oil going through this outlet, so that the flow of oil is permanently adapted to efficiently cool the piston, even if the pressure or the flow rate of the oil provided to the piston cooling jet varies.
According to further aspects of the invention, such a piston cooling nozzle might incorporate one or several of the following features:                The mechanical means include a deformable wall defining the shape of the piston cooling jet outlet, whereas this wall closes a chamber adapted to be fed with the fluid under pressure.        The wall surrounds the outlet of the nozzle.        The chamber surrounds the wall.        The wall is annular and located between the outlet and the chamber.        The chamber is annular.        An inlet conduit feeds fuel fluid under pressure to the chamber.        The inlet conduit is adapted to be connected to a source of the oil flow going through the outlet of the piston cooling jet.        An outlet conduit evacuates fluid under pressure from the chamber.        The outlet conduit is provided with a restriction device.        
The invention also concerns, according to an aspect thereof, a lubrication system for an internal combustion engine which comprises a pump feeding a main line, whereas an auxiliary line connects this main line to at least one nozzle, this auxiliary line being provided with first proportional means controlling oil flow within this line. This system is characterized in that it includes a control line connecting the main line or the auxiliary line, upstream of the first proportional means, to mechanical means adapted to control the outlet section of the nozzle on the basis of the pressure of oil delivered by the control line, whereas the control line is provided with second proportional means controlling the pressure of oil delivered to the mechanical means.
Thanks to an aspect of the invention, the second proportional means allow to actuate the mechanical means, via the pressure of oil delivered to these mechanical means, in order to adjust the outlet section of the nozzle.
According to further aspects of the invention, such a lubrication system might incorporate one or several of the following features:                The nozzle is as mentioned here-above.        The first and second proportional means are proportional valves controlling oil flow respectively within the auxiliary line and within the control line.        The proportional means are piloted independently.        The main line of the lubrication system provides oil to at least one support interface for a crankshaft of the engine.        
The invention also concerns, according to an aspect thereof, an internal combustion engine equipped with a nozzle as mentioned here-above or a lubrication system as mentioned here-above.